This invention relates generally to gas turbine engines and more particularly, to methods and apparatus for cooling a turbine blade trailing edge.
At least some known turbine engines include a core engine having, in serial flow relationship, a high pressure compressor which compresses an airflow entering the core engine, a combustor which ignites a mixture of fuel and compressed air to generate hot propulsive gases, and a high pressure turbine which is rotated by the hot propulsive gases. The high pressure turbine is connected to the high pressure compressor by a shaft such that the high pressure turbine blades drive the high pressure compressor. Additional compressors and turbine blades (e.g., a low pressure compressor and a low pressure turbine) may be positioned in serial flow relationship with the core engine.
Each turbine blade includes a pair of sidewalls that are connected at a leading edge and a trailing edge. The metal temperature distribution of a typical blade is such that the trailing edge of the blade is significantly hotter than the temperature of the bulk of the blade. The temperature gradient created may result in high compressive stress at the blade trailing edge, and the combination of high stresses and high temperatures may result in the blade trailing edge being the life limiting location of the blade.
Accordingly, within at least some known turbine blades, the blade trailing edge is cooled by a film of cooling air discharged from an internally-defined blade cavity. More specifically, the film of cooling air is discharged through a plurality of trailing edge slots formed on the airfoil pressure side, and upstream from the airfoil trailing edge. Specifically, known trailing edge cooling slots are cast in a row wherein each of the slots has the same length. As such, within known blades, the inlets of adjacent slots and the exits of adjacent slots are substantially radially aligned along the blade trailing edge. Although such slot orientations may be sufficient to satisfy blade mechanical and thermal requirements, such slot geometries may also mechanically weaken the blade near the inlets of some of the slots. For example, during operation, the weakened trailing edge area may develop undesirable vibratory stresses, which over time, may cause radial cracking and/or material losses within the blade trailing edge. Moreover, thin areas within the blade trailing edge may also increase the likelihood that a portion of the blade may fail due, at least in part, to high centrifugal stresses induced during operation.